I have a Food Saver and have used it for years. The trick with powdered foods is to keep them in the bag they came in. I have had more problems with flour gumming it up than anything else. I also blew the motor on mine this summer vacuum sealing my spinach, as I left too much water in and it leaked into the machine (I was not paying attention like I should). Many foods, like the spinach, is better off being frozen aahead of time, then put in a bag and sealed.
The biggest trick I've learned...or should I say the biggest mistake I've learned to avoid...is to label everything well and include the date!